Multiply digits of number of list python-CodePudding

I have array of 3 digit prime numbers:

for num in range(100, 1000):
     if num > 1:
         for i in range(2, num):
             if (num % i) == 0:
                 break
             else:
             numere_prime.append(num)

the list is:

numere_prime = [[101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163...]

What I need is multiply each digits of a number (ex 101 = 1 * 0 * 1) and then it shows all numere_prime that after multiplying is equal to user input. what i made so far:

    for elem in numere_prime:
        digits = [int(x) for x in str(elem)] # split digits into [1,0,1][1,0,3]...
        for n in list(digits):
            // n * n_at_next_index * n_at_next_index
            if //result of multiplying == //number set by input:
            //append digits to result list

result should be like:input (9) = [191, 313, 331, 911]

CodePudding user response：

Your prime algorithm is wrong. You can't just append to list when ANY factor fails, you have to know that ALL of the factors fail. And you don't have to search all the way to num; you only have to search up through sqrt(num). Since the largest value is 1000, you can stop at 33. Also, it's silly to check for num > 1 since you start the range at 100. And you don't have to convert digits to a list; it's already a list.

You could make this a bit shorter by using the any function inside get_primes, and by using yield in the filter_primes. You'll get to that later.

def get_primes():
    numere_prime = []
    for num in range(100, 1000):
        prime = True
        for i in range(2, 34):
           if (num % i) == 0:
              prime = False
              break
        if prime:
           numere_prime.append(num)
    return numere_prime

def filter_primes(primes, magic):
    res = []
    for elem in primes:
        digits = [int(x) for x in str(elem)] 
        product = 1
        for n in digits:
            product *= n
        if product == magic:
            res.append(elem)
    return res

numere_prime = get_primes()

inp = int(input("Your value: "))

result = filter_primes(numere_prime, inp)
print(result)

CodePudding user response：

primes = [101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163]
a = int(input('enter a nmber :'))
primes_useful = []
for i in primes :
    product = 1
    for k in str(i):
        product *= int(k)
    if product == a :
        primes_useful.append(i)

print(primes_useful)

CodePudding user response：

numere_prime = []
for num in range(100, 1000):
    prime = True
    for i in range(2, num):
        if (num % i) == 0:
            prime = False
    if prime:
        numere_prime.append(num)


def prime_digit_prod(x):
    output = []
    for elem in numere_prime:
        digits = [int(x) for x in str(elem)] # split digits into [1,0,1][1,0,3]...
        result = 1
        for n in digits:
            result *= n
        if result == x:
            output.append(elem)
    return output

print(prime_digit_prod(9))

output:

[191, 313, 331, 911]

CodePudding user response：

numere_prime = [101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157]
digi_mult_dict = {}
for elem in numere_prime:
    c = elem % 10
    b = int((elem % 100 - c)/10)
    a = int((elem - b - c)/100)
    mult = a * b * c
    digi_mult_dict[elem] = mult
numero = input("input a number")
for key, value in digi_mult_dict.items():
    if int(value) == int(numero):
        print(key)